We will prepare genomic and cDNA clones including MHC genes and cDNA products from mRNA for genes expressed in B cells, T cells and teratocarcinoma cells. We will then extend these genomic clones with the ultimate goal of obtaining the entire chromosomal region embedding the MHC complex in overlapping genomic clones. We will insert these cloned DNAs in plasmid and viral vehicles that will lead to the production of antigens in animal cells and/or in bacteria. We will characterize the DNA controlling the expresssion of gene products in different types of cells or cells at different stages of differentiation.